'In 1993, Atsushi Ohori extended the Standard ML of New Jersey compiler at Kansai Laboratory of Oki Electric, and named the experimental prototype SML# of Kansai. [..] The name SML# of Kansai symbolizes the field selector #〈label〉, which was given a polymorphic type for the first time by this compiler.'

http://www.pllab.riec.tohoku.ac.jp/smlsharp/docs/1.0/en/Ch1....

It predates it, actually.